#!/usr/bin/env Python
import time
import sys

if len(sys.argv) > 1:
    INTERFACE = sys.argv[1]
else:
    INTERFACE = 'eth0'
STATS = []
print('Interface:', INTERFACE)


def rx():
    ifstat = open('/proc/net/dev').readlines()
    for interface in ifstat:
        if INTERFACE in interface:
            stat = float(interface.split(':')[1].split()[0])
            STATS[0:] = [stat]


def tx():
    ifstat = open('/proc/net/dev').readlines()
    for interface in ifstat:
        if INTERFACE in interface:
            stat = float(interface.split(':')[1].split()[8])
            STATS[1:] = [stat]


print('In                     Out')
rx()
tx()

while True:
    time.sleep(1)
    rxstat_o = list(STATS)
    rx()
    tx()
    RX = float(STATS[0])
    RX_O = rxstat_o[0]
    TX = float(STATS[1])
    TX_O = rxstat_o[1]
    RX_RATE = round((RX - RX_O) / 1024 / 1024, 3)
    TX_RATE = round((TX - TX_O) / 1024 / 1024, 3)
    print(RX_RATE, 'MB              ', TX_RATE, 'MB')
